speakers efficiency

Assuming a listening distance of about 10 feet in a semi-reverberant room, a pair of 89 dB/1 watt efficient speakers will probably produce about 87 dB at the listening position with a 1 watt input. I can go through the math behind that figure if anyone's interested. From there the pattern follows the trend that Elevick detailed.

Real-world, thermal compression can be a significant issue and very few home audio speakers really give you a 10 dB increase in SPL for a tenfold increase in input power. Somewhere between 7 and 9 dB is more likely, depending on the speakers and the input power level. This is one of the main arguments in favor of high efficiency speakers using high quality prosound drivers - namely, that thermal compression is negligible at typical in-home listening levels, so dynamic contrast is improved.

Anyway to get back to your question, 89 dB/1 watt efficiency is slightly above average.

Now make sure that the manufacturer is really claiming 89 dB/1 watt. If it's a 4-ohm speaker, the manufacturer may be claiming 89 dB/2.83 volts. While 2.83 volts into 8 ohms is 1 watt, 2.83 volts into 4 ohms is actually 2 watts, so in the latter case the speaker would actually be only 86 dB/1 watt efficient.

And just for the record I'm misusing the term "efficiency" - to be precise "efficiency" should be expressed as a percentage or a decimal fraction, but I'm following industry convention here.

Duke

Myraj points out that I wasn't clear in something I said.

Let me try re-writing the second to last paragraph from my post above:

"Now make sure that the manufacturer is really claiming 89 dB/1 watt EFFICIENCY. If it's a 4-ohm speaker, the manufacturer may be claiming 89 dB/2.83 volts SENSITIVITY. While 2.83 volts into 8 ohms is 1 watt, 2.83 volts into 4 ohms is actually 2 watts, so in the latter case the speaker would actually be only 86 dB/1 watt efficient even though it's 2.83 volt sensitivity is 89 dB."

Hope that helps.

Duke

Bignerd, I don't really have any experience in pro-sound applications; I just have played around some (maybe too much) with prosound drivers.

I have no specific knowledge of the effect of a crowd on room acoustics. I'd guess a crowd of people would be more absorptive than diffusive, such that the power requirement to meet a given SPL in a full auditorium would be several dB more than if the room was empty. And since most absorbers are more effective at short wavelengths (high frequencies) than at long wavelengths (low frequencies), the spectral balance of the soundfield would be tilted downward somewhat by adding a crowd of people. But I have no idea of the specifics of such effects.

Duke